This invention relates to apparatus for, and methods of, depositing materials on a substrate. More particularly, the invention relates to apparatus for, and methods of, sputtering atoms from a target for a deposition of the sputtered atoms on a substrate. The invention provides for a sputtering of a considerably greater percentage of the material from the target than in the apparatus of the prior art.
Integrated circuit chips are formed from a plurality of layers. Some of the layers may be electrically insulating and other layers may be electrically conductive. Each of the layers may be formed by providing a magnetron to deposit atoms of a preselected material on a substrate. The preselected material may be obtained from a target formed from the preselected material, the target being disposed in a cavity.
Electrical and magnetic fields are provided in the cavity. Electrons in the cavity respond to the combination of the electrical and magnetic fields to ionize molecules of an inert gas introduced into the cavity. The gas ions are attracted to the target with a sufficient energy to sputter atoms from the surface of the target. The sputtered atoms become deposited on the substrate.
In order to provide an optimum efficiency in the sputtering of atoms from the target, the magnetic flux lines should extend through and also just above the target in substantially the same direction as the disposition of the target in the magnetic field. This has not occurred in the magnetrons of the prior art. As a result, only about thirty-five percent (35%) of the material has been sputtered from the targets in magnetrons of the prior art.
Targets are expensive. The sputtering from the targets of the prior art of approximately only thirty-five percent (35%) of the material in the targets represents a significant cost to an organization which is using the targets to deposit layers of material on a substrate. Furthermore, it is time-consuming, and therefore costly, to set up a magnetron to deposit a layer of material from a target on a surface of a substrate. It would accordingly be desirable to provide a magnetron in which substantially all of the material in a target is sputtered on the surface of a substrate.
An electric field is provided in a first direction between an anode and a target having a flat disposition. A magnetic field is provided by a magnet structure such that the magnetic flux lines are in a second direction substantially perpendicular to the first direction. The magnet structure may be formed from permanent magnets extending radially in a horizontal direction, like the spokes in a wheel, and from magnetizable pole pieces extending vertically from the opposite ends of the horizontally disposed permanent magnets. The horizontal permanent magnets and the vertical magnetizable walls define a well.
The target is disposed in the well so that its flat disposition is in the same direction as the magnetic flux lines. Molecules of an inert gas flow through the well. Electrons in the well move in a third direction substantially perpendicular to the first and second directions. The electrons ionize gas molecules. The ions are attracted to the target and sputter atoms from the surface of the target. The sputtered atoms become deposited on a substrate. Reflectors in the well near the radially outer magnetizable walls of the magnet structure, and also in one embodiment near the radially inner magnetizable walls of the magnet structure, prevent electrons from striking the magnet structure. The reflector(s) and the anode are cooled by a fluid (e.g. water).
The resultant magnetron sputters as much as 65% of the material from the target on the substrate in contrast to a sputtering of approximately 35% of the material from the targets on substrates in the prior art.